An employee died from antimony pentachloride (SbCl5) exposure on a chemical site after removing a plug from a 1-ton cylinder he believed to be empty. The substance is used as catalyst and becomes spent when contaminated by residual material from the reaction. A company in Colorado regenerates the spent catalyst and returns it fresh to the site.

The cylinder, containing used SbCl5 to be regenerated, was initially shipped from a sister plant of the same operator in California (that had been closed down since) to the facility in Colorado ; it was shipped as empty although its gross weight was 2 t. The cylinder was rejected by the regenerating company because it did not meet company specifications. Since the company had no formal procedure for handling rejected material, the cylinder was labelled and shipped as R-22 refrigerant gas (without positive identification of the contents) to the facility in Louisiana.

Upon arrival, the cylinder was neither tested nor weighted and the weight on the shipping document was not checked (the gross weight of a full R22 cylinder being 1.3 t and the arriving cylinder weighting 2 t, the check could have identified a problem). Furthermore, the cylinder -though full of material – was placed in the empty refrigerant cylinder storage area.

When the operator prepared the cylinder (which he believed empty of R22 refrigerant !) in order to send it to offsite testing, he used an impact wrench to remove a plug (valves could not open due to build-up of corrosion products) and was sprayed with its contents at 1:30 pm. Employees saw a large cloud in the ton-cylinder area and recognized the odour of antimony pentachloride; one employee sounded the plant alarm and activated the nearby water deluge towers to knock the vapours down. They assisted their colleague into an emergency shower for decontamination ; the man was sent to the hospital where he died the next day.

The cloud filled the area around the cylinder rack and was visible from offsite. Neighbours directly to the southeast of the facility noticed a strong odour. Plant employees were evacuated, and the plant emergency response team, dressed in appropriate personal protective equipment (PPE), entered the area to plug the cylinder.

The US CSB investigated the case and pointed out that :

1/ the company had no program to identify and address potential hazards in the ton-cylinder area. Procedures and training did not adequately prepare the ton-cylinder operator so that he could recognize a non-routine situation and its related SbCl5 cylinders, he likely did not know the difference between these cylinders (fitted only with fusible plugs) and refrigerant cylinders (fitted with at least one pressure relief valve).

2/ Neither companies had any systematic processes for positively verifying the contents of the cylinders, thus increasing the risks of mislabelling.

3/ The procedures for receiving ton cylinders were not adequate to identify abnormal cylinders and to prevent a full cylinder being placed in a area reserved for empty ones.

4/ Day-to-day operator practices and operator training did not conform to the standard operating procedures for handling R-22 cylinders that specified that R-22 cylinders should not be sent to the vent pipe at the ton-cylinder area. If work practices in this area had followed written procedures, the cylinder would not have been brought to the ton-cylinder area.

2 other accidents occurred on the same plant in less than 4 weeks (ARIA 23694 and 23081).